Corticobasal degeneration is a neurodegenerative disease affecting the cerebral cortex and basal ganglia of the brain. It is rare, affecting about five to seven out of every 100,000 people, and usually does not present until after the age of 60. Diagnosis is difficult, as corticobasal degeneration has symptoms similar to other neurodegenerative conditions, and can only be definitively diagnosed postmortem. There is currently no known cause of the disease.
Corticobasal degeneration is a slow, progressive disease, meaning that the brain gradually degenerates, causing symptoms to become worse over time. Symptoms include uncontrolled rhythmic muscle contractions, decreased movement, muscle rigidity, impaired balance, alien hand syndrome or the inability to sense and control the movements of the hand, apraxia or the inability to control the movement of the limbs, and aphasia or the loss of speech. Psychological and cognitive symptoms including irritability, dementia, and depression are also common. This cluster of symptoms is sometimes referred to as corticobasal syndrome (CBS) or corticobasal degeneration syndrome (CBDS), since definitive diagnosis of corticobasal degeneration is not possible while the patient is alive.
Imaging techniques including fluorodopa positron emission tomography (FDOPA PET), magnetic resonance imaging (MRI), and single photon emission computed tomography (SPECT) are sometimes used on a patient with CBS, though they are generally inconclusive. However, such techniques may allow for diagnosis of corticobasal degeneration in the future. FDOPA PET is used to diagnose impaired dopamine uptake in affected areas of the brain. MRI can identify atrophy, or wasting away, of structures in the brain, and SPECT examines perfusion or blood supply in the brain, which is usually reduced in patients with CBS.
Corticobasal degeneration is often misdiagnosed as progressive supranuclear palsy, Parkinson's disease, and various forms of dementia, including Alzheimer's disease. Frontotemporal dementia, a degenerative disease of the frontal and temporal lobes of the brain, can progress into CBS. While the symptoms of CBS do not line up exactly with any of these other conditions, allowing for some to be eliminated as possible causes in certain patients, not all possible symptoms are always present, and it is often impossible to completely rule out other diseases. There is no cure for CBS, and prognosis is very poor, with most patients dying within eight years. Treatment focuses on alleviating symptoms, and may include dopaminergic medication, as well as speech therapy to address aphasia and methods to help the patient move and eat.
Corticobasal degeneration can be diagnosed by a histological, or microscopic, examination of brain tissue. Unnaturally high levels of the protein tau, along with astroglial inclusions or abnormal outgrowths of the astrocytes, support cells of the brain, are indicative of the condition. The method most commonly used to detect these signs is the Gallyas-Braak staining method.